Niobium is the chemical element with the symbol Nb and the atomic number 41. A rare, soft, grey, ductile transition metal, niobium is found in the minerals pyrochlore, the main commercial source for niobium, and columbite. Niobium has physical and chemical properties similar to those of the element tantalum, and the two are therefore difficult to distinguish. The English chemist Charles Hatchett reported a new element similar to tantalum in 1801, and named it columbium. In 1809, the English chemist William Hyde Wollaston wrongly concluded that tantalum and columbium were identical. The German chemist Heinrich Rose determined in 1846 that tantalum ores contain a second element, which he named niobium. In 1864 and 1865, a series of scientific findings clarified that niobium and columbium were the same element (as distinguished from tantalum), and for a century both names were used interchangeably. The name of the element was officially adopted as niobium in 1949. It was not until the early 20th century that niobium was first used commercially. Niobium is used mostly in alloys, although alloys contain only a maximum of 0.1%, that small percentage of niobium improves the strength of the steel. The temperature stability of niobium-containing superalloys is important for its use in jet and rocket engines. Niobium is used in various superconducting materials. These superconducting alloys, also containing titanium and tin, are widely used in the superconducting magnets of MRI scanners. Other applications of niobium include its use in welding, nuclear industries, electronics, optics, numismatics and jewelry. In the last two applications, niobium's low toxicity and ability to be coloured by anodisation are particular advantages.
The metal takes on a bluish tinge when exposed to air at room temperature for extended periods. Despite presenting a high melting point in elemental form (2,468 °C), it has a low density in comparison to other refractory metals. Furthermore, it is corrosion resistant, exhibits superconductivity properties, and forms dielectric oxide layers. These properties— especially the superconductivity —are strongly dependent on the purity of the niobium metal. When very pure, it is comparatively soft and ductile, but impurities make it harder. The atoms of niobium is slightly less electropositive and smaller than the atoms of its predecessor in the periodic table, zirconium, while it is virtually identical in size to the heavier tantalum atoms which are subject to the lanthanide contraction. As a result, niobium's chemical properties are very similar to the chemical properties of tantalum, which appears directly below niobium in the periodic table. Although its corrosion resistance is not as outstanding as that of tantalum.
The base value of each unit of ranges between 10 and 20Ð per unit, with up to 6 units being found at any one time.
Presence on Mars: Common
|Group 1 | Group 2 | Group 3 | Group 4 | Group 5 | Group 6|
|Group 2|||Argon | Bromine | Cadmium | Gallium | Germanium | Gold | Helium III | Krypton | Molybdenum | Neon | Niobium | Nitrogen | |Palladium | Rhodium | Rubidium | Ruthenium | Scandium | Selenium | Silver | Strontium | Technetium | Titanium | Vanadium | |Yttrium | Zirconium||